Many applications exist in which it is desired to reduce ambient moisture by placing a desiccant in or near a particular area. These applications include such items as medical diagnostic test strips, food and medicine containers, and packaging materials.
A general method and apparatus used to position a desiccant near an object which is to be kept moisture-free involves the placement, near the object, of a pouch which contains a desiccant. In this conventional method, the pouch is made of a material which is water vapor permeable, and water vapor is allowed to permeate the pouch and be absorb ed by the desiccant inside the package. This method and apparatus allows loose desiccant, however, to exist inside the pouch. Such loose desiccant raises several potential problems.
The first problem is the risk of spillage of the desiccant if the pouch were to be punctured. That is particularly problematic where it is desired that the desiccant and material which is to be kept dry should not contact one another. It is also problematic where desiccant grains could interfere with, or contaminate, a nearby machine or material. A further risk involves ingestion of the desiccant. This is especially likely if the desiccant pouch application involves food or medicine. All of these risks are associated with the use of desiccants loosely contained inside a permeable pouch.
A second potential problem with the above use involves the difficulty which exists in placing an exact amount of desiccant in close proximity to the material to be kept dry where the material or its location is very small and difficult to reach. Often, where pouches of desiccant material are used, or loose desiccant material is glued to a surface, packages must be modified to accommodate the bulk desiccant. Where that arrangement is necessary, packaging inefficiencies are present. Also, in such cases, alternative methods and devices must be used to place the desiccant effectively.
Medical diagnostic test strips are used, for example, in a variety of applications. Such strips are exposed to samples of blood, feces, or urine, for example, where specific reagents on the test strip are designed to detect various components in the sample. Medical diagnostic test strips are specifically used to detect the level of glucose in a patient's blood. Such test strips must be exposed to an atmosphere that is substantially moisture-free until moments before use in testing a sample. The strips are often highly water absorbent, and absorption of moisture may alter test results.
Accordingly, the known industry practice for keeping the test strips dry is to contain a plurality of such test strips in a container or vial. The cap for the container has a desiccant contained in it to absorb water from the air inside the container. In this manner, the strips within the container are kept dry. When ultimately used, a doctor or other testing personnel, including a patient himself removes the cap from the container, extracts one of the test strips, and immediately places it in the sample to be tested (or places a small quantity of the sample to be tested on the test strip). Exposure of the strips to the ambient atmosphere before use is thus minimized to reduce water vapor absorption by the test strip.
Potential problems with this are many, but include the difficulty associated with the placement of the desiccant into the cap. Some methods which have been developed to achieve desiccant placement in this configuration include gluing the desiccant gel into a lid, or actually constructing a cap out of a desiccant-containing plastic. These methods are specialized, however, and often require difficult manufacturing techniques.
The deficiencies of the conventional desiccant applications show that a need still exists for a desiccant technology which allows precise, controlled, and easy placement of the desiccant in a location and in an amount which is desired. Therefore, one object of the present invention is to provide a desiccant technology which allows easy, precise, and controlled placement of a desiccant into small areas. Another object of the present invention is to provide a desiccant technology which allows easy placement of a consistent and controlled amount of desiccant over a large area. Yet another object of the present invention is to provide a desiccant technology which allows a user to apply a desiccant through simple devices. Still another object of the present invention is to provide a desiccant technology which allows the use of a desiccant in close proximity to other materials without the risk of loose desiccant falling free and causing subsequent problems.